1. Field of the Invention
The present invention relates generally to adjustable clamps for holding workpieces during various machining operations, and more particularly to a rapid acting clamp which employs a quick set/quick release cam carried by a sliding dovetail joint to improve its clamping action.
2. Description of the Prior Art
Devices for securely retaining workpieces during machining operations are well known in the machining arts, and have a long history of development. Over the years a great deal of inventive energy has been devoted to devices for holding workpieces, and basic V-blocks and related holding structures, continue to be among the most utilized due to their versatility and ruggedness. Similarly, a wide array of clamping devices have been developed for rigidly retaining the range of workpiece sizes and shapes in their associated V-blocks. A number of U.S. Patents teach methods and apparatus for clamping workpieces in V-blocks, or similar workpiece holders, and are reflective of the amount of ingenuity which this field has attracted. Generally, these prior art clamping devices have employed a plurality of threaded screws to bear against a like plurality of workpiece surfaces to anchor it in its associated V-block. For example, U.S. Pat. No. 4,201,376 to Philips discloses an adjustable clamp which includes an array of three threadedly adjustable clamping screws, two or more of which are manually screwed down to engage the workpiece surfaces. The unused screw is presumably moved out of the way, and two of these three screw members are movable in slots to provide a measure of flexibility in their workpiece engaging adjustments.
In another U.S. Pat. No. 3,358,990 to Anton, there is disclosed an earlier V-block clamp employing a pair of threadedly adjustable screw members carried by structures permitting a degree of slideable adjustment. As with the '990 patent described above, two of the three screw members are adjusted to engage two distinct surfaces of the workpiece.
In the December 1946 edition of what appears to be the American Machinist Magazine, a simplified cousin of the screw down V-block clamps described in aforementioned two U.S. Patents is pictured. As illustrated there, the simpler device employs a single screw down member carried by a slideable member to achieve its workpiece holding action.
These prior art clamping devices, and others, operate more or less well and have found wide usage within the nation's machine shops. Virtually all of these prior art devices, however, require a multiplicity of individual adjustments to intially clamp the workpiece in position, and a like multiplicity of reverse steps to release the workpiece on completion of the desired machining. The same sequence of manipulations must be carried out for each and every workpiece to be handled. When used in one-of-a-kind machining applications, these repetitive steps are merely a time consuming inconvenience. But, when used where a significant number of similar workpieces are to be machined--a very common situation in small to medium size production machine shops--the loss in man hour productivity is significant. This loss leads to undesirably high unit costs for the finished articles, and represents poor utilization of a skilled machinist's time, not to mention the expensive milling/grinding machine time lost. It's not difficult to see that devices as basic as a workpiece clamp can make a major contribution to overall machining efficiency, and so setup times are constantly under scrutiny to avoid losses incurred by needless repetitive steps. Therefore, it is clear that a continuing need exists for a quick acting clamp which will provide reliable and positive clamping action while greatly reducing the time required to initially set up the clamp; apply and tighten the clamp members; thereafter releasing the clamp; and subsequently preparing the clamp/V-block for the insertion of the next workpiece. The improved quick action cam-lock clamp taught in the present invention admirably meets these needs with great precision.